Tendomers - force sensitive bis-rotaxanes with jump-like deformation behavior

Area of Science:

• Supramolecular Chemistry
• Polymer Physics
• Materials Science

Background:

• Tendomers are formed from rotaxane molecules with sliding rings, creating a confined 'real gas' system.
• Understanding the mechanical response of such complex molecular architectures is crucial for designing novel materials.

Purpose of the Study:

• To investigate the mechanical response of tendomers under external pulling forces.
• To analyze the interplay between polymer chain deformation and the compression of confined slide rings.
• To explore the potential of tendomers as molecular-elastic elements with tunable properties.

Main Methods:

• Theoretical analysis using the exact partition function, accounting for ring repulsion and finite chain extensibility.
• Comparison of theoretical models with Monte Carlo simulation data for tendomers under force.
• Development of a simplified thermodynamic approach to elucidate the underlying physics.

Main Results:

• Tendomers exhibit a critical pulling force (∝ (m/N)1/2) leading to a jump-like decrease in elasticity (strain-softening).
• At low forces, tendomers behave like short polymer chains; beyond the critical force, they behave like longer chains.
• A strong peak in mechanical susceptibility is observed at the critical force, characteristic of a phase transition.
• Asymmetric tendomers allow for multi-step force-extension curves, enabling precise control over mechanical responses.

Conclusions:

• Tendomers function as molecular-elastic elements with predictable, jump-like strain-softening behavior.
• The ability to design multi-step force-extension curves makes tendomers promising for tailor-made stress-sensitive elastomers.
• This study provides fundamental insights into the mechanics of complex supramolecular systems.